In system virtualization, multiple virtual systems are created within a single physical system. The physical system can be a stand-alone computer, or alternatively, a computing system utilizing clustered computers and components. Virtual systems are independent operating environments that use virtual resources made up of logical divisions of physical resources such as processors, memory and input/output (I/O) adapters. This system virtualization is implemented through some managing functionality, typically hypervisor technology. Hypervisors, also called virtual machine managers (VMMs), use a thin layer of code in software or firmware to achieve fine-grained, dynamic resource sharing. Because hypervisors provide the greatest level of flexibility in how virtual resources are defined and managed, they are the primary technology for system virtualization.
The hypervisor provides the ability to divide physical system resources into isolated logical partitions (also referred to as LPARs). Each logical partition operates like an independent system running its own operating environment (i.e., a virtual system). Exemplary operating environments include AIX®, IBM® i, Linux®, and the virtual I/O server (VIOS). The hypervisor can allocate dedicated processors, I/O adapters, and memory to each logical partition. The hypervisor can also allocate shared processors to each logical partition. Unbeknownst to the logical partitions, the hypervisor creates a shared processor pool from which the hypervisor allocates virtual processors to the logical partitions as needed. In other words, the hypervisor creates virtual processors from physical processors so that logical partitions can share the physical processors while running independent operating environments.
The hypervisor can also dynamically allocate and deallocate dedicated or shared resources (such as processors, I/O, and memory) across logical partitions while the partitions are actively in use. This is known as dynamic logical partitioning or dynamic LPAR. This allows the hypervisor to dynamically redefine all available system resources to reach optimum capacity for each partition.
In addition to creating and managing the logical partitions, the hypervisor manages communication between the logical partitions via a virtual switch. To facilitate communication, each logical partition may have a virtual adapter for communication between the logical partitions, via the virtual switch. The type of the virtual adapter depends on the operating environment used by the logical partition. Examples of virtual adapters include virtual Ethernet adapters, virtual Fibre Channel adapters, virtual Small Computer Serial Interface (SCSI) adapters, and virtual serial adapters.
Virtual adapters are often implemented through a VIOS partition which manages the physical I/O adapters (SCSI disks, Fibre Channel disks, Ethernet, or CD/DVD optical devices). The other logical partitions may be considered “clients” or virtual I/O clients (VIOCs) to the VIOS. The VIOS can provide virtualized network resources to the other logical partitions via a Shared Ethernet adapter (SEA). The SEA bridges a physical Ethernet adapter with the respective virtual adapters and may apportion network bandwidth.
In the event that one of the logical partitions is terminating abnormally, or crashing, an operating system (OS) image dump process is performed during which diagnostic data about the terminating logical partition is collected, compressed, and written to a storage device. The time that it takes to perform the OS image dump process may, for example, take anywhere from several minutes to an hour to complete. Typically, a number of processors, memory, and I/O resources allocated to the terminating logical partition continue to be used during the OS image dump process.